Re: [PATCH net v3] bonding: Fix unnecessary warnings and logs from bond_xdp_get_xmit_slave()

Paolo Abeni
2024-09-24T10:20:47Z

On 9/18/24 16:06, Jiwon Kim wrote:
> syzbot reported a WARNING in bond_xdp_get_xmit_slave. To reproduce
> this[1], one bond device (bond1) has xdpdrv, which increases
> bpf_master_redirect_enabled_key. Another bond device (bond0) which is
> unsupported by XDP but its slave (veth3) has xdpgeneric that returns
> XDP_TX. This triggers WARN_ON_ONCE() from the xdp_master_redirect().
> To reduce unnecessary warnings and improve log management, we need to
> delete the WARN_ON_ONCE() and add ratelimit to the netdev_err().
>
> [1] Steps to reproduce:
> # Needs tx_xdp with return XDP_TX;
> ip l add veth0 type veth peer veth1
> ip l add veth3 type veth peer veth4
> ip l add bond0 type bond mode 6 # BOND_MODE_ALB, unsupported by XDP
> ip l add bond1 type bond # BOND_MODE_ROUNDROBIN by default
> ip l set veth0 master bond1
> ip l set bond1 up
> # Increases bpf_master_redirect_enabled_key
> ip l set dev bond1 xdpdrv object tx_xdp.o section xdp_tx
> ip l set veth3 master bond0
> ip l set bond0 up
> ip l set veth4 up
> # Triggers WARN_ON_ONCE() from the xdp_master_redirect()
> ip l set veth3 xdpgeneric object tx_xdp.o section xdp_tx
>
> Reported-by: syzbot+c187823a52ed505b2257@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=c187823a52ed505b2257
> Fixes: 9e2ee5c7e7c3 ("net, bonding: Add XDP support to the bonding driver")
> Signed-off-by: Jiwon Kim <jiwonaid0@gmail.com>

Isn't the above issue completely addressed by explicitly checking for
bond->prog in bond_xdp_get_xmit_slave()? Or would that broke some use-case?

Thanks,

Paolo